These systems work as follows&colon; When a pre-defined pollution degree is reached&comma; the backflushing automatically starts&period;Then the contaminations from the screen pack are led out of the machine via a spillway&period; The contaminated backflush mass leaves the machine by means of heated backflush outlet pipes which are installed at the screen changer housing&period; There the small quantity may be removed or collected&period;

With the-channel screen changers additional slide valves are used at the backflush channels&period; There is no interference of the process during backflushing&period;

Features included1&comma;Continuously working melt filter2&comma;Four working stations 3&comma;venting groove can discharge the gas mixed in the raw material 4&comma; no interference during the process of backflushing5&comma;the screen cleaning reached 85&percnt;6&comma; long life span of the filtration screen pack&sol;mesh &comma; it owning to up to 100 times backflushing at most&period;screen change procesThe screen changer and gas venting process of this kind of Automatic backflush screen changer with four working positions for plastic extrusion machineThe following process is based on standing face to the screen changer and extruderone rod is pushed out on the left side of the housing of the screen changer by hydraulicallythe blocked filter screen pack is removed and replaced by a fresh onethe rod is pushed into the housing of the screen changerthis rod is pushed out on the rignht side of the housing of the screen changer by hydraulically&period;the other one blocked filter screen pack on this rod is removed and replaced by a fresh one&period;the other rods repeat the above stepsThe gas venting systen begins to work when the rod is pushed into the housing of the screen changer&comma; and the following picture show the process of gas venting of this type of dual rods continuous extrusion screen changer for polymer melt filtration&period;